The present invention relates to rotary head type magnetic recording and reproducing devices such as rotary head type digital audio tape recorders (RDAT) and video tape recorders (VTR), and more particularly, to a rotary head type magnetic recording and reproducing device having a high speed searching function.
In a VTR or RDAT, a rotary head is used to record data on a magnetic tape run at a fixed speed and to reproduce the data. In a RDAT in which a magnetic tape 3.8 mm in width is wound on a rotary drum 30 mm in diameter for 90.degree. and mainly digital audio signals are recorded or reproduced (sometimes, however, still picture signals or other data may be recorded or reproduced), a particular part of one inclined track is employed as a sub-code area where data other than audio digital data to be recorded or reproduced, such as time data (hours, minutes and seconds) and data indicative of the order of musical selections, are recorded, and the data thus recorded is reproduced in a high speed searching operation. Two sub-code areas each, corresponding to an angle of 1.degree. to 4.degree. out of the winding angle 90.degree., are provided in one track.
The tape winding angle of such a device, as mentioned above is 90.degree., namely, smaller than that of an ordinary VTR. Therefore, the magnetic tape can be run at high speed while being wound on the drum. However, the device suffers from a diffuculty that, when the magnetic tape is run in the forward and reverse directions a high speed 200 times (1.44 m/s) the fixed speed (7.22 mm/s) and with the speed of the drum maintained constant (2000 rpm), the relative speed of the magnetic head and the magnetic tape differs greatly depending on the direction the tape is run. While the relative speed is about 3.1 m/s in the fixed speed running operation, in the high speed running operation, the relative speed is about 4.6 m/s in the reverse direction and about 1.7 m/s in the forward direction. Accordingly, in the high speed searching operation, even with one and the same signal, the reproduction frequency greatly differs depending on the tape running direction, which makes it difficult to process the signal.
Reproduction of the sub-code data can be done only at the rate of one sub-code data area per about 200 tracks on the magnetic tape. Therefore, it is impossible to perform the searching operation finely, and the sub-code data is not read out at a fixed period. Furthermore, for the same reason, the device used for extracting only the sub-code data from the reproduced data, including data other than the sub-code data, is necessarily intricate.
As shown in FIG. 1, in the fixed speed running operation, the locus ((a) in FIG. 1) of the magnetic head 1 on the magnetic tape 2 forms an angle of about 6.38.degree. (being the angle of inclination of the inclined track). On the other hand, in the high-speed, forward-direction running operation (fast forwarding operation) the locus forms an angle of about 11.7.degree. (as indicated at (b) in FIG. 1) because the relative speed is decreased. Moreover, in the high-speed reverse-direction running operation (the rewinding operation) the locus forms an angle of about 4.3.degree. because the relative speed is increased. Accordingly, in the high-speed running operation (in the searching operation) the trace angle changes, not only when the magnetic tape is run in the forward direction, but also when it is run in the reverse direction, and the magnetic head traces the magnetic tape obliquely over a plurality of tracks. As a result, the sub-code data is reproduced from the sub-code area 3 over several tracks, which still further makes it difficult to process the signal.